The use of metering valves for water faucet have many potential advantages over the conventional manually operated valves. A metering valve closes automatically after it allows a predetermined quantity of water flow. This special feature can result in water saving by reducing excessive water running and also by eliminating water running unattended due to user negligence or vandalism.
In many commercial and public buildings metering valves are installed for hand washing faucets. A typical design of existing metering valves has a push button on the top of the valve body. Once the button is pushed down, the water flow starts and it continues for a short moment and then stops automatically. The user has to first push button at the top of the valve to start a wash cycle and then move his hand, while the water is running, to the position underneath the valve, in order to receive the water. By doing so, a portion of water is wasted before the user can reach the running water. Normally the vale is adjusted to run only for a very short period. Frequently, the water stops in the middle of hand washing. Therefore, the user has to reach the top of the valve and push the button again. This not only wasted a lot water in between, but causes inconvenience to the users, transfers germs and also soils the valves with soap residues. Most users have various frustrating experiences with existing metering valves and this is the primary reason that metering valves have not been popular in spite of its potential advantages.
To better benefit the user and save water, it is most desirable that the water could be triggered at a suitable location, such as near the running water, so that the hand would be ready to receive water right at the start of water flow. If the water stops in the middle of hand washing, the cycle should be able to restarted conveniently and without removing the hand from its washing position. Then, the water can be fully utilized and, at the same time, the other inconveniences with conventional metering valves can be eliminated.